The present invention relates to a support with an adjustable length, which is used particularly for chairs, tables or the like, having an essentially tubular casing, and internal components, whereby at least one annular seal belongs to these components.
Supports of this type are already known. The outer or peripheral surface of the respective end piece is essentially cylindrical. The diameter of this outer surface is somewhat smaller than the inside diameter of the tubular main body of the casing. Consequently, a gap exists between the outer surface of the end piece and the interior surface of the casing. Inside of the support, cavities and channels are carried out, whereby said channels connect the cavities together. Therein is a fluid, i.e. a gas or a liquid, for example oil, and said fluid can stream therein. In order to prevent, that the fluid can leave the casing of the support, seals are placed in the gap between the cylindrical outer surface of the respective end piece and the cylindrical interior surface of the also cylindrical casing.
The pressure of the fluid in the inside of the support can reach extraordinary high values, so that seals of the column in the support must fulfill extraordinary high quality requirements. The respective seal is made as a ring of a yielding material, as for example of rubber or plastic. In the cylindrical peripheral surface of the end piece a circular groove is carried out, in which the sealing ring is partly embedded, so that a part of the sealing ring projects from the groove.
During the assemblage of the known support, the components of the support, to which the end piece with the sealing rings also belong, are put into the casing in the direction of the longitudinal axis. Thereby that one section of the sealing ring, which is protuberant from the groove, glides on and along the interior surface of the casing. If the interior surface of the casing shows unevennesses like ridges, dirt, etc., then the surface of the outer section of the sealing ring, which is protuberant from the ring-groove, can be damaged by said unevennesses. This can affect the quality of the seal of the inside of the support with respect to its surrounding. In order to avoid such a damage for the seals, the interior surface of the casing must be completely smooth and clean. Such a smooth surface can be reached by polishing the inside wall of the casing, for example. Said polishing of the interior surface of the casing is not quite simple and moreover, this polishing is an additional and time-consuming operation. Absolute cleanliness during assembly of the supports is not always easy.
The object of the present invention is, to eliminate the mentioned and even further inconveniences of the foreknown supports.
This object is achieved according to the present invention in the case of the support of the generic type mentioned in the beginning of this specification.
In the following, embodiments of the present invention are explained on the basis of the enclosed drawings in more detail. It shows: